Johns Hopkins University (JHU) requests funding for the establishment of a Central Laboratory (CL) for the HIV Prevention Trials Network (HPTN). The JHU CL will be affiliating with the Coordinating and Operations Center (CORE) at Family Health International in Durham, NC and the Statistical and Data Management Center SDMC) at the Fred Hutchinson Cancer Research Center in Seattle, WA. Specific aims are the following: 1. Provide laboratory based scientific leadership and consultation to the HPTN collaborating organization and protocol teams. 2. Participate in the HPTN protocol development and review process. 3. Participate in the network management and establishment of the HPTN scientific agenda. 4. Provide processing, storage, and retrieval of domestic and international HPTN trial specimens. 5. Provide quality assurance for specimen processing, assay performance, and specimen related data transmission performed at the HIV Prevention Trial Unit (HPTU) sites. 6. Provide training and infrastructure support in laboratory QA, assay performance, and specimen shipping procedures at the HPTU clinical site laboratories. 7. Perform immunologic, pharmacologic, and virologic/bacteriologic testing for the HPTN protocols. 8. Develop and evaluate new assays for use in HPTN trials. 9. Coordinate procedures and timely transmission of accurate lab data to the HPTN SDMC. 10. Publish findings of new assay development/evaluation and pathogenesis based studies. To optimize the amount of scientific expertise and lab capabilities needed, the HPTN CL will be based on a hub and spoke concept involving JHU, University of Pittsburgh, and the California Public Health Dept (VRDL).